The embodiments described herein relate generally to an electric machine, and more specifically, to a wire guide associated with the electric machine.
An electric machine is typically in the form of an electric generator or an electric motor. The machine typically has a centrally located shaft that rotates relative to the machine. Electrical energy applied to coils within the motor initiates this relative motion which transfers the power to the shaft and, alternatively, mechanical energy from the relative motion of the generator excites electrical energy into the coils. For expediency the machine will be described hereinafter as a motor. It should be appreciated that a motor may operate as a generator and vice versa.
A stationary assembly, also referred to as a stator, includes a stator core and coils or windings positioned around portions of the stator core. It is these coils to which energy is applied to initiate this relative motion which transfers the power to the shaft. These coils are formed by winding wire, typically copper, aluminum or a combination thereof, about a central core to form the winding or coil.
In an assembled configuration the coils are positioned in a spaced apart relationship about the stationary assembly that typically has a generally hollow cylindrical configuration with the coils positioned internally. The power of the electric motor is dependent on the amount of energy that may be applied to the coils and that amount of energy is proportional to the amount of wire that may be positioned about the stationary assembly. The amount of wire positioned about the stationary assembly is typically referred to as the slot fill. Placing as much wire in the coils as possible, also known as maximizing the slot fill is thus desirable.
Of many methods of manufacturing the stator and winding the wire to form the coil in particular, the following three methods are typical. The first is to form a rigid hollow cylindrical core with internal protrusions of teeth around which the coils are wound. The core is typically produced by stacking a plurality of rigid hollow laminations and joining them to form the rigid hollow cylindrical core. This method requires the wire to be fed around the teeth with a device called a needle. The need to provide for movement of the needle around the teeth limits the amount of wire that may be used to form the coil.
A second method is to similarly form a rigid hollow cylindrical core with internal protrusions of teeth and to provide spools or bobbins that may be removably secured to the teeth of the core. The coils are formed by winding wire around the coils while separated from the stator and then by assembling the wound bobbins onto the teeth of the stator. The separated coils provide improved access around the coil to more completely form the coil.
A third known method of manufacturing a stationary assembly includes stacking a plurality of laminations and rolling the stack to form a round stator. The laminations are stamped from a sheet of stock material and stacked to form a substantially linear array of stator sections and connecting members. The substantially linear array includes a first end and a second end. Teeth are formed along one side of the linear array. Windings may be wound on the stator sections around the teeth while the laminations are in the linear orientation in a configuration where the linear array of laminations are arched with the teeth positioned outwardly. Once the windings are positioned on the stator sections, the stack is formed into a second shape. To form the stack into the second shape, the stack is rolled around a central axis and the first end is coupled to the second end with the teeth positioned inwardly. The second shape is the substantially round shape of a stator. Typically, the second shape is maintained by securing the first end to the second end. The linear arrays provide improved access around the teeth to more completely form the coil.
Regardless of which method is used to form the coil, maximizing the amount of wire (also known as maximizing the slot fill or wire density) includes uniformly winding the wires in a plurality of layers around the teeth. Wires in each layer are preferably positioned abutted against each other and the wire in any layer is preferably cradled between adjacent wires in the layer below that layer of wire. This arrangement of wires to form the coils is typically called a precision arrangement and is preformed with a precision wire laying process. Providing this arrangement and maintaining the proper tension on the wires while providing high speed automated assembly has been a challenge.
Other arrangements of the wires are typically called random windings. With such random windings, the tight abutting relationship of wires within a layer is not maintained. For example, the wires have difficulty tracking in the cradle formed between adjacent wires and may tend to separate from the wires on which the wire above is cradling, permitting wires in an upper layer to migrate into the space between the wires of the lower layer. This migration of the wires causes the wires of upper layers to cross over the wires of the lower layers at random locations, creating bulges in the coil and less complete or inferior slot fill. The present invention is directed to alleviate at least some of these problems with the prior art.